A container used in a water server etc. is often a container molded using a polycarbonate (PC) resin having high strength as a raw material. However, since the container made of this polycarbonate resin has low flexibility, large space is required in a case of storing an empty container.
Because of this, a container having flexibility, which is molded of a softer raw material, has become widespread (for example, see Patent References 1 and 2). According to this soft container, at the time of storage or discard, the volume of the container can be reduced and further, at the time of use, the container is naturally crushed under atmospheric pressure with an outflow of liquid. Therefore, it is unnecessary to introduce air into the inside with a reduction in liquid, and the container is superior from a hygiene standpoint. However, since this soft container has low durability alone, it is difficult to handle the container in a state filled with the liquid.
Hence, a so-called bag-in-box for supplementing the durability of the container by storing the soft container in an outer box made of a cardboard box is developed (for example, see Patent Reference 3). In this bag-in-box, normally, the container is taken out of the outer box, and the container is installed by inserting the container into a box-shaped storage part of a water server from above with a mouth part provided on an upper portion of the container turned downwardly.